A pyrrolizidine alkaloid, retroisosenine occurs in the basic extract of Senecio nemorensis. It
crystallizes as colourless rods from EtOH and is dextrorotatory with a specific rotation of
[α]D24 + 118°(c 0.69, CHCl3).The ultraviolet spectrum in EtOH consists of a single absorption maximum at 220nm.
